Glass fibers have hitherto been added to polycarbonate order to improve its rigidity and dimensional stability. The addition of the glass fibers, however, makes the polycarbonate subject to brittle fracture and lowers the Izod impact strength. Thus, a variety of polycarbonates have been investigated for the purpose of finding the one which is excellent in impact resistance. For instance, the blending of a polycarbonate with a filler and an organopolysiloxanepolycarbonate block copolymer has been proposed in Japanese Patent Application Laid-Open No. 160052/1980, but such blending is still unsatisfactory for improving the impact resistance.
Also, a composition which comprises blending a polycarbonate with a glass fiber free of a sizing agent and a siloxane has been proposed in Japanese Patent Application Laid-Open (PCT application) No. 501860/1982. Furthermore, in Japanese Publication No. 35929/1984, there has been proposed a composition comprising a polycarbonate with a glass fiber and an organopolysiloxane having a specified viscosity. However, the molded articles produced from these two compositions have also a problem of incomplete insulation.